(1) Field of the Invention
The present invention relates generally to an ultrasonic piezoelectric transducer, and more particularly, to an ultrasonic piezoelectric transducer and an ultrasonic actuator which generate ultrasonic oscillation or vibration by utilizing an electro-mechanical energy conversion element such as a piezoelectric element, an electric distortion element or the like.
(2) Related Art Statement
The conventional ultrasonic piezoelectric transducer of the kind referred to above, for example, has been disclosed in Japanese Patent Laid-Open No. 7875/1990. The piezoelectric transducer comprises a piezoelectric laminated body in which an upper table for transmitting an oscillation or vibration output is provided at one end surface of a piezoelectric laminated member comprising a plurality of plate-like piezoelectric elements stacked upon each other. A lower table serving as a substrate is provided at the other end surface of the piezoelectric transducer, and a pair of piezoelectric elements are provided on opposing side surfaces of the piezoelectric laminated body. Means for controlling synthesis or composition of vibration generated by the piezoelectric laminated body and vibration generated by the pair of piezoelectric elements to vibrate the upper table in a desired direction are provided. Specifically, as shown in FIG. 17 of the attached drawings, the ultrasonic piezoelectric transducer is arranged such that a laminated piezoelectric element 2 comprising plurality of stacked piezoelectric elements is fixedly mounted on an upper surface of a resonator 1, and piezoelectric elements 3a and 3b of bimorph type are adhered to and fixedly mounted respectively on opposing side surfaces of the resonator 1. An upper base 4 is fixedly mounted on an upper surface of the laminated piezoelectric element 2, and a projection 5 is provided on the upper base 4. When the ultrasonic piezoelectric transducer is activated, alternating voltages shifted in phase 90 degrees from each other are applied to the laminated piezoelectric element 2 and the piezoelectric elements 3a and 3b. Vibration components in a longitudinal direction and in a lateral direction are composed with each other, and a composing condition is controlled, to cause the projection 5 to undergo elliptic vibration or inclined reciprocal vibration in which a material point on the piezoelectric transducer has an optional magnitude and an optional mode or aspect.
However, the conventional ultrasonic piezoelectric transducer discussed above has a problem, in that it is difficult to sufficiently obtain an appreciable amplitude in a Y-direction (in a bending or curving direction) upon resonance. This is due to the fact that, since the piezoelectric elements 3a and 3b of the bimorph structure are used in driving in the Y-direction, it is impossible to reduce the thickness T of the resonator as far as possible in view of the structure thereof. For this reason, the rigidity of the resonator per se is raised or increases, so that there cannot be a sufficient bending motion.